1. Field of the Invention
This invention relates to a method of manufacture of a semiconductor device, and to a semiconductor device, electro-optical device, integrated circuit, and electronic equipment manufactured by this method.
2. Description of the Related Art
In an electro-optical device, such as for example a liquid crystal display device or an organic EL (electroluminescence) display device, pixel switching and similar is performed using thin film circuits which are configured comprising thin film transistors as semiconductor elements. In a thin film transistor of the prior art, a channel formation region or other active region is formed using amorphous silicon film. Thin film transistors have also been employed in which polycrystalline silicon film is used to form an active region. By using polycrystalline silicon film, the mobility and other electrical characteristics are improved compared with elements using amorphous silicon film, and the performance of the thin film transistor can be enhanced.
In order to further improve the performance of thin film transistors, technology has been studied in which a semiconductor film comprising large crystal grains is formed, such that crystal grain boundaries do not intrude into the channel formation region of the thin film transistor. For example, a technique has been proposed in which, by forming a minute hole (depression) in a substrate, and using this hole as a starting-point for crystal growth to crystallize a semiconductor film, silicon crystal grains with large grain diameters are formed. Such a technique is described in, for example, Japanese Patent Laid-open No. 11-87243, in the reference “Single Crystal Thin Film Transistors”, IBM Technical Disclosure Bulletin, August 1993, pp. 257–258, and in the reference “Advanced Excimer-Laser Crystallization Techniques of Si Thin-Film for Location Control of Large Grain on Glass”, R. Ishihara et al, proc. SPIE 2001, vol. 4295, pp. 14–23. By forming a thin film transistor employing silicon film with large crystal grain diameters formed using this technique, it is possible to prevent crystal grain boundaries from intruding into a formation region (in particular, the channel formation region) of one thin film transistor. By this means, thin film transistors can be realized with excellent mobility and other electrical characteristics.
When forming a thin film transistor for use in applications where comparatively large currents are passed, the width of the channel formation region (channel width) is set to be large when forming the thin film transistor. For example, in a buffer circuit to output a signal, and particularly in a buffer circuit to select a scan line in a liquid crystal display device or organic EL device, thin film transistors with large channel widths are used. When setting large channel widths in this way also, it is desirable that the thin film transistor be formed such that crystal grain boundaries are not included in the channel formation region.
However, the crystal grain diameters of silicon films which can be formed using the techniques described in the above references are several microns approximately, so that when silicon film is formed on a substrate, crystal grain boundaries exist in intervals of at least several microns approximately in the silicon film. Consequently when attempting to form a thin film transistor in which the channel width is set to be larger than this, crystal grain, boundaries existing in the channel longitudinal direction traverse the channel formation region, so that crystal grain boundaries are included in the channel formation region, and so impede efforts to further improve the characteristics of the thin film transistor.
Hence this invention has as an object the provision of a semiconductor device manufacturing method enabling the fabrication of a thin film transistor which is little affected by crystal grain boundaries, even when the channel width of the thin film transistor is made larger than the crystal train boundaries of the semiconductor material.
Also, this invention has as an object the provision of a semiconductor device enabling a thin film transistor with comparatively large output current, and with satisfactory charge mobility and other characteristics.